Biofuels are an alternative for fossil fuels. For example, isobutanol can be used as a high octane fuel for four-stroke internal combustion engines, as a pure component or in any portion as a mixture with gasoline. It has a high energy density (36 MJ/Kg) and low heat of vaporization (0.43 MJ/Kg), both of which satisfy the requirements (energy density≧32 MJ/Kg, heat of vaporization<0.5 MJ/Kg) specified by this FOA. The research octane number of isobutanol is 110, which also satisfies the requirement (>85).